Thanks for reviewing! I've updated the patch according to your comments. Best regards, Peifeng Qiu
On Sun, Apr 7, 2019 at 2:31 PM Noah Misch <n...@leadboat.com> wrote:
> On Sat, Mar 30, 2019 at 03:42:39PM +0900, Peifeng Qiu wrote:
> > When I watched the whole build process with a task manager, I discovered
> > that a lot of time was spent on generating export symbol definitions,
> > without consuming much CPU or IO.
> > The script that doing this is src/tools/msvc/gendef.pl, it enumerates
> the
> > whole directory for ".obj" files and call dumpbin utility to generate
> > ".sym" files one by one like this:
> >
> > dumpbin /symbols /out:a.sym a.obj >NUL
> >
> > Actually the dumpbin utility accepts a wildcard file name, so we can
> > generate the export symbols of all ".obj" files in batch.
> >
> > dumpbin /symbols /out:all.sym *.obj >NUL
> >
> > This will avoid wasting time by creating and destroying dumpbin process
> > repeatedly and can speed up the build process considerably.
> > I've tested on my 4-core 8-thread Intel i7 CPU. I've set MSBFLAGS=/m to
> > ensure it can utilize all CPU cores.
> > Building without this patch takes about 370 seconds. Building with this
> > patch takes about 200 seconds. That's almost 2x speed up.
>
> I, too, get a strong improvement, from 201s to 149s. I can confirm it
> yields
> identical *.def files. Thanks for identifying this improvement.
>
> > - my ($objfile, $symfile) = @_;
> > - my ($symvol, $symdirs, $symbase) = splitpath($symfile);
> > - my $tmpfile = catpath($symvol, $symdirs, "symbols.out");
>
> You removed the last use of File::Spec::Functions, so remove its "use"
> statement.
>
> > - system("dumpbin /symbols /out:$tmpfile $_ >NUL")
> > - && die "Could not call dumpbin";
>
> This error handling was crude, but don't replace it with zero error
> handling.
>
> > - rename($tmpfile, $symfile);
>
> Keep the use of a temporary file, too.
>
> > +system("dumpbin /symbols /out:$symfile $ARGV[0]/*obj >NUL");
>
> That should be *.obj, not *obj.
>
generate-symbols-in-batch-on-windows-v2.patch
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